Single level spine fusion procedures typically entail removing the intervertebral disk and inserting an interbody device into the disk space. Current spine fusion procedures rely heavily on the use of posterior fixation to achieve the stability and rigidity necessary to obtain successful clinical results. However, implantation of posterior instrumentation necessarily involves removing important musculoskeletal elements. Because of these concerns, anterior fixation systems have also been developed which require removal of much less musculoskeletal mass. However, because anterior fixation, especially in the abdominal or thoracic area, lies in close proximity to vital internal organs (e.g., the aorta), these fixation systems must also possess a low profile.
In general, conventional intervertebral connection systems can be characterized by ligament components that are either: (1) relatively rigid; or (2) not shaped for cooperative connection to bone anchors; or (3) by bone anchors that are shouldered to seat upon the vertebral surface. When the ligament is relatively rigid, it must essentially lie fully upon the anterior surfaces of the adjacent vertebrae, thereby limiting design options. Systems having relatively rigid ligaments typically have transverse holes near their end portions for accepting bone anchors. In systems in which the ligament is not shaped for cooperative attachment to the bone anchor, attachment is typically made by either suturing or by passing a screw through the ligament. When the bone anchor is seated upon the vertebral surface, a portion of the bone anchor protrudes from the surface and the tension of the ligament cannot be further adjusted.
In commonly-owned U.S. patent application Ser. No. 09/822,126, entitled “Intervertebral Connection System”, filed Mar. 30, 2001, and incorporated herein by reference, there is disclosed an intervertebral connection system comprising a ligament having a central portion, first and second end portions, first and second conformable portions, and first and second shoulderless bone anchors (see U.S. Patent Publication No. US2002/0143329 A1, dated Oct. 3, 2002, which publication is also incorporated herein by reference). The shoulderless feature of the bone anchor allows the bone anchor to be fully driven into the vertebral surface, thereby eliminating any problematic protrusion while also providing a means to adjust the tension of the ligament after the bone anchors have been located. The conformable portions of the ligament allow the ligament to conform to the recess produced by a fully driven bone fastener without generating undue stress, thereby accommodating the surgeon's desire to fully drive the bone fastener within the recess. The cooperative shape of the ligament end portions allows for non-destructive attachment of the ligament to the bone anchors without the use of sutures, thereby minimizing unwanted connection-related stresses and undesirable generation of foreign particles within the patient.
In commonly-owned U.S. patent application Ser. No. 10/112,619, entitled “Expandable Cable Anchor”, filed Mar. 29, 2002, and incorporated herein by reference, there is disclosed a bone anchoring device for securing suture or cable within a bone hole. The bone anchoring device includes a radially expandable sheath, an expander member for expanding the sheath, and a washer. As disclosed in the application, two bone anchoring devices could be connected via a cable and used to hold a bone block between adjacent vertebrae in spinal fusion procedures.
Bone anchors for attaching soft tissue or sutures to bone are well known in the art. Also well known in the art are inserter tools for deploying such bone anchors in a hole in bone tissue. All of the known art describes deployment of a single anchor to secure a structure to bone.
In the case of multiple anchor surgical constructs, such as the intervertebral connection system described above, there is a need for an inserter that can simultaneously deploy a plurality of bone anchors. More specifically, an inserter is needed wherein a surgical construct, comprising two or more anchors connected by a ligament or cable, can be readily assembled to the inserter for delivery and simultaneous deployment of the anchors into holes in bone.